Project Summary/Abstract The goal of this Pathway to Independence Award (K99/R00) application is to obtain training in the cognitive neuroscience of flexible cognitive control and brain network analysis from expert researchers in preparation for independence, where this training will be used to start a laboratory that investigates the network mechanisms of flexible control. Flexible control - a capacity supporting adaptive, goal-directed behavior important in daily life - is affected in a variety of mental illnesses, markedly reducing quality of life. Critically, the mechanisms underlying flexible control remain poorly understood at both cognitive and neural levels. A large body of evidence suggests that flexible control is implemented across a variety of situations by a set of fronto-parietal brain regions sometimes referred to as the cognitive control network (CCN). We recently found that CCN regions have among the highest global brain connectivity (GBC) in the human brain and, more importantly, that GBC in a lateral prefrontal CCN region strongly predicts fluid reasoning - suggesting flexible control is linked to the global connectivity properties of specific brain regions. Based on these findings, we postulate the flexible hub hypothesis: that some CCN regions are able to use their extensive connectivity to flexibly reconfigure currently active connections (with task-relevant sensory, semantic, and motor regions) according to task demands. We will investigate the hypothesis that flexible hubs are a key neural mechanism underlying flexible control by determining the neural network and cognitive properties underlying the relationship between flexible hubs and flexible control. During the mentored (K99) phase I will receive training in graph theory from Dr. Steve Petersen (co-mentor), Dr. Olaf Sporns (collaborator), and Dr. Deanna Barch (collaborator) to enable the development of more quantitatively precise network property indicators that can identify and define flexible hubs in the human brain. Further, training in individual differences approaches from Dr. Todd Braver (mentor) and Dr. Randall Engle (collaborator) will enable the development of more quantitatively precise cognitive measures of flexible control. During the independent (R00) phase we will then build upon this research and training to determine how dynamic (across-task) flexible hub connectivity changes are related to stable network properties and flexible control abilities. This rigorous characterization of the link between flexible hubs and flexible control will enable a more comprehensive understanding of the flexible control impairments present in a variety of mental illnesses. Training will take place at Washington University in St. Louis, which has extensive intellectual and equipment resources for conducting studies of executive functions involving individual differences and functional connectivity magnetic resonance imaging (fcMRI). Dr. Braver is a world expert in cognitive control research and has extensive experience using individual differences methodology with functional MRI, which makes him an excellent mentor for the proposed training plan. Dr. Petersen is a world expert in developing graph theory fcMRI methods and applying them to cognitive control research, makes him an excellent co-mentor for the proposed training plan. Importantly, several well-established collaborators will also supplement my training and evaluation during the K99 phase and the transition into the independent R00 phase. I have pursued my interest in researching the cognitive neuroscience of executive functions since I was an undergraduate in Mark D'Esposito's laboratory at UC Berkeley. I subsequently went to graduate school in Walter Schneider's laboratory at the University of Pittsburgh and received a Ph.D. in Neuroscience. My graduate research led to multiple first-authored publications based on innovative research approaches driven by my strong independent research interests. Specifically, these interests led me to focus primarily on two lines of research: rapid instructed task learning (RITL) and GBC. The first, RITL, investigates the executive functions underlying flexible, adaptive human behavior (i.e., flexible cognitive control). This is important and timely research as it remains a mystery how healthy individuals are able to rapidly (i.e., in a single trial) learn a virtually infinite variety of possible tasks (and how this ability can become impaired in mental illnesses). For instance, this ability is used the first time an individual uses a cell phone (in order to adapt to differences from 'landline' phones), or any new technology. The second line of research, GBC, is focused on characterizing the brain's most connected regions. My time as a postdoctoral fellow in Dr. Braver's lab has been highly productive, as I have learned new advanced fMRI methods such as multivariate pattern analysis (MVPA), developed a new RITL cognitive paradigm, and published a paper investigating GBC deficits in schizophrenia, among other accomplishment. Critically, the proposed research plan will combine - and benefit from synergy between - the RITL and GBC lines of research in preparation for forming my own independent laboratory. I plan to develop my laboratory primarily at the confluence of these two lines of research: investigating the ways in which brain network connectivity specifies the dynamics underlying flexible cognitive control. The training and research outlined in this K99/R00 proposal are essential components of my career development plans as I transition to becoming a successful independent researcher.